It has worked, sites like 'webmasterworld' have done these things in the past.

If you have a niche audience, that's loyal - you can segment the site and charge a membership fee.

It's a tricky line to walk, you'll need something of value to offer the 'premium' users without upsetting the free users be excluding them too much.

The best method would be to segment one particular subject first, see how that goes - and move on from there.